This invention relates to methods and apparatus for delivery of medicament to the respiratory system of a patient. In particular, the invention relates to apparatus and methods of this type for use in association with a nebulizer.
It is known to use a nebulizer to create an aerosol of medication for delivery into the respiratory system of a patient. Typically the medication is placed in a cup which is held over a reservoir of buffer water. A piezoelectric element is vibrated ultrasonically under the buffer water transferring energy to the water, thus causing an aerosol to be formed in the medication cup. Baffles are provided between the medication cup and the airway in an attempt to ensure large particles of medication rain out on the filter and drip back down into the medication cup.
These nebulizers suffer from a number of disadvantages. In particular, medications have a range of different viscosities, however particle generation is not consistent across the range. Thus the medication particle size is not accurately controlled and a broad range of particles pass into the patient airway. Nebulized medication which rains out on the filter drips back into the cup only to be nebulized again. This may degrade or destroy the medication.
The medication in the cup is directly exposed to the airway. Therefore the nebulizer must be maintained substantially horizontal at all times to prevent medication spilling out into the patient airway. Also the ventilator pressure will be lost when the medication cup is removed to refill it.
This method of aerosol generation requires a relatively large amount of energy, the response time of aerosol generation is thus large. A considerable amount of heat is generated during use of the nebulizer, therefore to prevent patient discomfort or injury the nebulizer is placed away from the patient. However this necessitates a long inhalation tube between the nebulizer and the patient, increasing drug loss through rain out along the inhalation tube, and further increasing the response time to patient inspiration. Further, the generated heat degenerates the medication, which can be particularly harmful to protein based drugs.
Hence, this invention is related to apparatus and techniques for delivery of medicament to the respiratory system of a patient.
In one embodiment, an apparatus for delivery of medicament to the respiratory system comprises a reservoir, such as a medication cup, for receiving a liquid medication that is to be delivered to a respiratory system. The apparatus also includes an aerosol generator that may be held within a housing. A liquid supplier is provided to deliver the liquid medicament from the cup to the aerosol generator. A connector is employed to receive aerosol generated by the aerosol generator. The connector has an aerosol inlet for receiving aerosol from the generator, an air inlet, and an outlet. In this way, the aerosol that is received through the aerosol inlet may be entrained with a gas passing through the air inlet, and the entrained aerosol may pass through the outlet for delivery to a patient. Conveniently, the connector may be coupled to a ventilator to introduce the gas into the air inlet.
In one aspect, the connector is of generally T-shape and has an inlet leg with a longitudinal axis and an outlet leg with an air inlet end and an aerosol outlet end. The inlet is connected to the outlet leg intermediate the air inlet end and the aerosol outlet end, and the outlet leg has a first portion extending from the air inlet end to the connection to the inlet leg. The first portion has a longitudinal axis, with the longitudinal axis of the inlet leg subtending an angle of less than 90xc2x0 with the longitudinal axis of the first portion of the outlet leg. Preferably the angle between the longitudinal axis of the first portion of the outlet leg and the longitudinal axis of the inlet leg is less than 80xc2x0. Ideally the angle between the longitudinal axis of the first portion of the outlet leg and the longitudinal axis of the inlet leg is about 75xc2x0. In some cases, the outlet leg may have a second portion extending from the first portion, the second portion being substantially in line with the first portion.
Conveniently, the connector may also be defined in terms of a gas conduit having an inlet, and an outlet, and an aerosol supply conduit. With such a configuration, the aerosol generator is configured to provide the aerosolized liquid medicament into the gas conduit through the aerosol supply conduit, and the gas conduit is adapted to pass gases to entrain the aerosolized liquid medicament.
In another embodiment of the invention, the medication cup is releasably mounted to the aerosol generator housing. In one aspect, the medication cup has a reservoir for holding a medication and a delivery tube having an inlet for receiving medication from the reservoir. The delivery tube is associated with the liquid supplier to deliver the liquid medication to the aerosol generator. The inlet may comprise a number of inlet slots which are circumferentially spaced-apart around the delivery tube.
The aerosol generator housing and the medication cup may be configured to be sealed to each other. This may be accomplished using a sealing mechanism, such as a skirt extending from the aerosol generator housing to sealingly engage the medication cup. Conveniently, the skirt may have an angled surface to sealingly engage a chamfered mouth of the medication cup. In a further aspect, the liquid supplier may be mounted to the aerosol generator housing.
In a further embodiment, the medication cup has a base with support for supporting the cup in an upright orientation when receiving liquid medication. The support may comprise a support skirt extending from the base of the cup. Conveniently, the medication cup may include a central well from which the delivery tube extends.
In one embodiment, the apparatus includes controller for controlling the operation of the aerosol generator. For example, the controller may send control signals to actuate the aerosol generator just prior to initiating an inhalation cycle of a ventilator and to deactivate the aerosol generator just after termination of the inhalation cycle of the ventilator. Conveniently, the controller may be the same controller used to control the ventilator. In one aspect, the aerosol generator housing has a signal connector to which a control signal from the controller is inputted to control the operation of the aerosol generator. An interface may also be used to interface the aerosol generator with the controller. The interface may be mounted remote from the aerosol generator housing.
In another aspect, the liquid supplier is mounted to the aerosol generator housing. In this way, the liquid supplier and the aerosol generator are configured as a single unit. In a further aspect, the medication cup may be releasably mounted to the aerosol generator housing. As such, the medication cup may easily be removed when refilling and/or replacement is needed.
According to another embodiment of the invention, a connector is provided for delivery of medicament to the respiratory system. The connector comprises a generally T-shaped device having an inlet leg with a longitudinal axis and an outlet leg with an air inlet end and an aerosol outlet end. The inlet leg is connected to the outlet leg intermediate the air inlet end and the aerosol outlet end. The outlet leg has a first portion extending from the air inlet end to the connection to the inlet leg. The first portion has a longitudinal axis subtending at an angle of less than 90xc2x0 with the longitudinal axis of the inlet leg.
In one aspect, the angle between the longitudinal axis of the first portion of the outlet leg and the longitudinal axis of the inlet leg is less than 80xc2x0. Ideally, the angle between the longitudinal axis of the first portion of the outlet leg and the longitudinal axis of the inlet leg is about 75xc2x0. The outlet leg may have a second portion extending from the first portion, with the second portion being substantially in line with the first portion.
In another embodiment, the invention provides a medication cup for receiving liquid medication for delivery to an aerosol generator. The medication cup has a reservoir for holding a medication and connector for connection to an aerosol generator. The medication cup has a releasable seal for maintaining the medication in the cup.
In one embodiment of the invention, the releasable seal comprises a sealing sheet releasably attached to the cup. Conveniently, a peel tab or other release mechanism may be used to remove the sheet. Alternatively the release mechanism may be a tab or other opener to perforate the sealing sheet when the cup is connected to the aerosol generator. The sheet may conveniently have an identifying code.
The invention further provides a nebulizer system for use with a ventilator circuit. The system comprises at least one tubing section having an inlet and an outlet for delivering air or other gases to a patient from a ventilator. The system further includes a nebulizer which delivers a nebulized fluid to the tubing section for inhalation by a patient on the ventilator. The nebulizer has a vibrating element having a front side, a back side and a plurality of openings. A fluid delivery system is employed to deliver fluid to the back side of the vibrating element. With this configuration, vibration of the vibrating element moves fluid from the back side of the vibrating element through the plurality of openings to produce the nebulized fluid which enters the tubing section for delivery to the patient.
In one aspect, the tubing section forms an air path and the source of fluid is separated from the air path by the vibrating element. In another aspect, the tubing section includes a T-shaped section. Conveniently, the source of fluid may include a capillary feed system which provides fluid to the back side of the vibrating element, and the vibrating element may comprise a ring-shaped piezoelectric element. The openings in the vibrating element may be sized to eject liquid droplets such that about 70% or more of the droplets by weight have a size in the range from about 1-5 micrometers.
In a further embodiment, a nebulizing device comprises a nebulizing element, and a fluid delivery system to deliver a fluid to the nebulizing element. At least one tube section is employed to define a delivery path to the patient. This delivery path is conveniently defined by a distance between the nebulizing element and the patient, and has a length of less than 500 mm, and preferably less than about 300 mm.
In one aspect, the nebulizing element has a vibrating element with openings therein. The vibrating element also has a front side and a back side, and the delivery path is defined at one end by the front side of the vibrating element. With this configuration, the fluid is delivered through the openings in the vibrating element upon vibration of the vibrating element, with the fluid being delivered to the back side of the vibrating element.
In another aspect, the tube section includes a T-shaped section having a top section and a central section, and the nebulizing element is positioned at a bottom of a central section. Ideally, the central section forms an angle of from 60xc2x0 to 80xc2x0 with a straight portion of the T-shaped section. In a further aspect, the tube section may include a Y-shaped section which separates into a first arm for inhalation and a second arm for exhalation. With this arrangement, the nebulizing element is coupled to a second tube section which is connected to the Y-section. Desirably, the second tube section is a T-shaped section which is attached to the Y-section. Preferably, the delivery path through the tube section is substantially free of baffles and flow disrupters.
The invention also provides a method of providing a nebulized fluid to a patient. According to the method, a vibratable member having a plurality of apertures that is in contact with a fluid is vibrated to produce a nebulized fluid. The nebulized fluid is permitted to eject into a conduit that is coupled to a ventilator. A gas from the ventilator is then employed to supply the aerosolized fluid to the patient""s airway. Alternatively, the nebulized fluid may be provided to the patient using other techniques, such as by patient inhalation.
In one aspect, the distance between the vibratable member and the patient is less than about 500 mm, and in some cases less than about 300 mm. In this way, minimal tubing may be used to supply the aerosolized fluid to the patient, thereby requiring less energy to nebulize the fluid and reducing the generated heat so that the medication is not compromised.
The invention further provides a ventilator circuit that comprises a nebulizing element, and a fluid delivery system for delivering fluid to the nebulizing element. A ventilator is used to deliver and withdraw air from a patient. A control system is operably coupled to the nebulizing element and the ventilator. The control system is used to activate the nebulizing element during an inhalation cycle where respiratory gases are being supplied to the patient by the ventilator. For example, the controller may activate the nebulizing element within about 20 milliseconds of initiation of an inhalation cycle and deactivate the nebulizing element within 20 milliseconds of termination of the inhalation cycle. In this way, the aerosol is generated essentially only when gases are being supplied to the patient.
In one aspect, the nebulizing element has a vibrating element with openings therein, and a front side and a back side. The fluid is delivered through the openings in the vibrating element upon vibration of the vibrating element, and the fluid is provided to the back side of the vibrating element.